In stark, often chilling congressional testimony on Thursday, an official with a relief organization responding to the Ebola crisis in West Africa labeled efforts to control the virus a failure.

Ken Isaacs, a vice president with Samaritan’s Purse, a North Carolina-based Christian humanitarian organization, also said the number of Ebola cases and deaths reported by the World Health Organization are probably 25 percent to 50 percent below actual levels.

During testimony before a subcommittee of the House Committee on Foreign Affairs, Isaacs told lawmakers that volunteers in the affected countries were in dire need of enhanced international support, including aircraft equipped to transport Ebola patients, more laboratories to speed the processing of blood tests and more security for health workers who face violence and a lack of cooperation from distrustful villagers.

Isaacs told of a prominent Liberian doctor who “openly mocked the existence of Ebola” by trying to enter a hospital isolation ward with no gloves or protective clothing. He and another man who accompanied him to the hospital both died within five days, Isaacs said.

At one point, Isaacs even disputed the earlier testimony of a physician from the U.S. Agency for International Development, who said his agency had provided 35,000 protective suits for health care workers in West Africa.

Isaacs told lawmakers he had received an email in the last 90 minutes from a hospital in Liberia “asking us for more personal protection gear. This a problem everywhere,” he said.

Prior to the current outbreak, Ebola had collectively stricken 2,232 people and claimed 1,503 lives in 32 years, Isaacs testified.

“Easily this present outbreak is going to surpass that in fatalities, as well as overall cases,” he said. “It is clear to say that the disease is uncontained and it is out of control in West Africa. The international response to the disease has been a failure and it is important to understand that.”

As of Thursday, WHO reported that the Ebola crisis ravaging Guinea, Liberia, Sierra Leone and Nigeria had killed 932 people, with 1,711 confirmed and suspected cases.

“Our epidemiologists and medical personnel believe that these numbers represent 25 to 50 percent of what is happening,” Isaacs testified.

Ebola only spreads through contact with infected bodily fluids. It cannot be transmitted through airborne particles. But there is no cure or treatment for the virus, which has a death rate of roughly 60 percent.

The U.S. Centers for Disease Control and Prevention has estimated it will take three to six months to contain the outbreak, which many believe will worsen before it improves.

On Thursday, the Food and Drug Administration modified a clinical hold on an experimental Ebola drug made by Tekmira Pharmaceuticals of Canada. The move allows the potential use of the drug, TKM-Ebola, on people infected with the virus.

While support from other African countries is slowly building, Isaacs said the lack of international assistance was evident for weeks as Samaritan’s Purse and Doctors Without Borders, another volunteer medical relief organization, were the only agencies providing clinical care to Ebola patients in the region.

“It was not until July 26 when Kent Brantly and Nancy Writebol were confirmed positive that the world sat up and paid attention,” Isaacs told the panel, which met even though Congress is officially in recess until early September.

Writebol, 59, a missionary from Charlotte, N.C., and Brantly, a 33-year-old physician from Fort Worth, Texas, are both in Emory University Hospital in Atlanta after contracting Ebola while treating patients in Liberia. Both were part of a missionary response team sponsored by Samaritan’s Purse and another relief organization, SIM USA.

As haggard volunteer medical workers struggle to treat the growing numbers of infected villagers, Isaacs said, the international community ignores the growing outbreak at its own peril.

“A broader coordinated intervention of the international community is the only thing that will slow the size and the speed of the disease,” Isaacs said.

He said that unless the international community gets involved, “the world will be effectively relegating the containment of this disease that threatens Africa and other countries to three of the poorest nations in the world.”

In earlier testimony, Rep. Frank Wolf, R-Va., said the Obama administration had also underestimated the scope of the outbreak and was noticeably absent in the early days of the response. He said the CDC couldn’t say who was in charge of the response or what actions were being taken and didn’t have a list of U.S. facilities that could treat Ebola patients if necessary.

“Little action was taken to get out in front of this problem, and now we’re seeing the results,” Wolf said.

After the hearing, White House National Security Council spokesman Patrick Ventrell countered those assertions.

“We have been engaged on this outbreak since March, when the first cases were reported, and have expanded our efforts over the last several weeks in response to the increased severity of the outbreak,” he said. “Both the World Health Organization and the CDC have announced that they will be surging personnel to these countries to assist in this effort.”

CDC Director Tom Frieden told lawmakers that the agency is sending 50 staffers to help with testing, public education and disease control. He said that if the three West African countries had invested in their medical infrastructure and followed protocol to contain the illness, the outbreak would have been contained.

Although Frieden explained that the disease is not easily transmitted, his testimony wasn’t completely reassuring to the panel. When asked if the disease could be transmitted on a plane by droplets from an infected person’s sneeze, Frieden was a bit noncommittal.

“In medicine we often say, ‘Never say never,’” Frieden told lawmakers, adding later, “We do have concerns that there could be transmissions from someone who’s very ill.”

If an infected person had no symptoms of the disease, they couldn’t pass the virus by sneezing or coughing, Frieden said.

“But if someone became ill on the plane and was having fever or started bleeding, for example, that might present a risk to those who came in contact with that and didn’t take appropriate precautions,” Frieden said.

Federal funding for pandemic preparedness planning has fallen from $201 million in fiscal 2010 to $72 million in 2014, according to Rep. Chris Smith, R-N.J., chairman of the subcommittee. The proposed funding for fiscal 2015 is $50 million. President Barack Obama’s fiscal 2015 budget calls for $45 million to fund global health security efforts.

While several experimental Ebola treatments are in the early stages of development, Frieden said, “We don’t want any false hopes out there. Right now, we don’t know if they work and we can’t, as far as we know, have them in any significant numbers,” since rapid mass production isn’t possible.

“We might or might not have effective and available treatment in three months or six months or one year or five years, but we today have the means to stop the outbreaks,” Frieden said, referring to efforts to identify, isolate and treat infected people and their contacts.

Lesley Clarke and John Moritz of the Washington Bureau contributed to this story.